1. Field of the Invention
The present invention relates to electronic apparatuses and control methods for the electronic apparatuses, and more particularly relates to a power supply control technology for a portable electronically-controlled timepiece including a built-in power generating device.
2. Description of the Related Art
Recently, small electronic timepieces, such as wristwatches, provided therein with a power generator, such as a solar battery, which can operate without replacing a battery have been realized. These electronic timepieces are provided with a function of accumulating power generated by the power generator in a large-capacitance capacitor or the like. When power is not generated, power discharged from the capacitor is used to indicate the time. Therefore, these timepieces can stably operate for a long period of time without a battery. Taking into consideration the burden of replacing or discarding a battery, it is expected that in future many timepieces will be provided therein with a power generator.
The timepieces including the power generator can be constructed as follows in order to stably supply power to a drive circuit of the timepieces. Electrical energy generated by the power generator is accumulated in a large-capacity power supply (for example, a secondary battery). A voltage of the secondary power supply is accumulated in a small-capacity power supply (for example, a capacitor) via a step-up/down circuit including a step-up/down capacitor for increasing or decreasing the voltage of the secondary power supply. Subsequently, the voltage is supplied to the drive circuit.
In the transition from a step-up/down state in which the voltage is increased or decreased through the step-up/down capacitor to a direct coupling state in which the large-capacity power supply is directly coupled to the small-capacity power supply, it is probable that charge (electrical energy) is suddenly transferred from the large-capacity power supply side to the small-capacity power supply side, or from the small-capacity power supply side to the large-capacity power supply side in accordance with the relative voltage relationship between the large-capacity power supply and the small-capacity power supply.
In such cases, a sudden variation occurs in the voltage supplied to the drive circuit of the small-capacity power supply. This may cause malfunctioning in the drive circuit or a control circuit.
Accordingly, it is an object of the present invention to provide an electronic apparatus and a control method for the electronic apparatus in which malfunctioning in a drive circuit or a control circuit is prevented in the transition from a step-up/down state to a direct coupling state.
A first embodiment of the present invention is characterized by including a power generating unit for performing power generation by converting first energy into second energy which is electrical energy; a first power supply unit for accumulating the electrical energy obtained by the power generation; a power supply voltage converting unit for converting the voltage of the electrical energy supplied from the first power supply unit by a voltage-conversion multiplying factor M (M is a positive real number); a second power supply unit, to which the electrical energy accumulated in the first power supply unit is transferred through the power supply voltage converting unit, for accumulating the transferred electrical energy; a driven unit driven by the electrical energy supplied from the first power supply unit or the second power supply unit; and a non-voltage-converting transfer control unit for transferring, in the transition from a state in which the electrical energy is being transferred from the first power supply unit to the second power supply unit through the power supply voltage converting unit by a voltage-conversion multiplying factor Mxe2x80x2 (Mxe2x80x2 is a positive real number except for one) to a state in which the first power supply unit and the second power supply unit are electrically directly coupled, the electrical energy from the first power supply unit to the second power supply unit through the power supply voltage converting unit by the voltage-conversion multiplying factor M=1 in a non-voltage-converting state, wherein a potential difference between the first power supply unit and the second power supply unit is less than a predetermined potential difference.
A second embodiment of the present invention is characterized in that, in the first embodiment, the electrical energy transfer to the second power supply unit is performed in an accumulating cycle for accumulating the electrical energy from the first power supply unit in the power supply voltage converting unit and a transfer cycle for transferring the electrical energy accumulated in the power supply voltage converting unit to the second power supply unit. The non-voltage-converting transfer control unit includes a number-of-transfers control unit for changing, when the accumulating cycle and the transfer cycle are repeated, the number of transfers which is the number of transfer cycles per unit time based on the electrical energy transfer ability required.
A third embodiment of the present invention is characterized in that, in the second embodiment, the number-of-transfers control unit determines the number of transfers based on power consumed by the driven unit.
A fourth embodiment of the present invention is characterized by including, in the third embodiment, a power consumption detecting unit for detecting the power consumed by the driven unit.
A fifth embodiment of the present invention is characterized in that, in the second embodiment, the number-of-transfers control unit includes a number-of-transfers storage unit for storing beforehand the numbers of transfers corresponding to a plurality of driven units, and a number-of-transfers determining unit for determining the number of transfers to be read from the number-of-transfers storage unit by referring to the driven unit to be actually driven from among the plurality of driven units.
A sixth embodiment of the present invention is characterized in that, in the second embodiment, the power supply voltage converting unit includes a step-up/down capacitor for performing voltage conversion. The number-of-transfers control unit determines the number of transfers based on the capacitance of the step-up/down capacitor.
A seventh embodiment of the present invention is characterized in that, in the second embodiment, in a single transfer cycle, when a transferable electrical energy amount is expressed by Q0, the number of transfers per unit time is expressed by N, and power consumed by the driven unit per unit time is expressed by QDRV, the number-of-transfers control unit determines the number of transfers per unit time N so as to satisfy the following expression:
QDRVxe2x89xa6Q0xc3x97N
An eighth embodiment of the present invention is characterized in that, in the first embodiment, the non-voltage-converting transfer control unit includes a unit for inhibiting, when the electrical energy is being transferred to the second power supply unit in the non-voltage-converting state, driving of a high load during a transfer for inhibiting driving of the driven unit that consumes power exceeding power corresponding to electrical energy which can be supplied in the transfer.
A ninth embodiment of the present invention is characterized in that, in the first embodiment, the driven unit includes a timer unit for indicating the time.
In a tenth embodiment of the present invention, there is provided a control method for an electronic apparatus including a power generator for performing power generation by converting first energy into second energy which is electrical energy; a first power supply for accumulating the electrical energy obtained by the power generation; a power supply voltage converter for converting the voltage of the electrical energy supplied from the first power supply by a voltage-conversion multiplying factor M (M is a positive real number); a second power supply, to which the electrical energy accumulated in the first power supply is transferred through the power supply voltage converter, for accumulating the transferred electrical energy; and a driven unit driven by the electrical energy supplied from the first power supply or the second power supply. The control method is characterized by including a non-voltage-converting transfer control step of transferring, in the transition from a state in which the electrical energy is being transferred from the first power supply to the second power supply through the power supply voltage converter by a voltage-conversion multiplying factor Mxe2x80x2 (Mxe2x80x2 is a positive real number except for one) to a state in which the first power supply and the second power supply are electrically directly coupled, the electrical energy from the first power supply to the second power supply through the power supply voltage converter by the voltage-conversion multiplying factor M=1 in a non-voltage-converting state, wherein a potential difference between the first power supply and the second power supply is less than a predetermined potential difference.
An eleventh embodiment of the present invention is characterized in that, in the tenth embodiment, the electrical energy transfer to the second power supply is performed in an accumulating cycle for accumulating the electrical energy from the first power supply in the power supply voltage converter and a transfer cycle for transferring the electrical energy accumulated in the power supply voltage converter to the second power supply. The non-voltage-converting transfer control step includes a number-of-transfers control step of changing, when the accumulating cycle and the transfer cycle are repeated, the number of transfers which is the number of transfer cycles per unit time based on the electrical energy transfer ability required.
A twelfth embodiment of the present invention is characterized in that, in the eleventh embodiment, the number-of-transfers control step determines the number of transfers based on power consumed by the driven unit.
A thirteenth embodiment of the present invention is characterized by including, in the twelfth embodiment, a power consumption detecting step of detecting the power consumed by the driven units.
A fourteenth embodiment of the present invention is characterized in that, in the eleventh embodiment, the number-of-transfers control step includes a number-of-transfers determining step of determining, from among the pre-stored numbers of transfers corresponding to a plurality of driven units, the number of transfers by referring to the driven unit to be actually driven.
A fifteenth embodiment of the present invention is characterized in that, in the eleventh embodiment, the power supply voltage converter includes a step-up/down capacitor for performing voltage conversion. The number-of-transfers control step determines the number of transfers based on the capacitance of the step-up/down capacitor.
A sixteenth embodiment of the present invention is characterized in that, in the eleventh embodiment, in a single transfer cycle, when a transferable electrical energy amount is expressed by Q0, the number of transfers per unit time is expressed by N, and power consumed by the driven unit per unit time is expressed by QDRV, the number-of-transfers control step determines the number of transfers per unit time N so as to satisfy the following expression:
QDRVxe2x89xa6Q0xc3x97N
A seventeenth embodiment of the present invention is characterized in that, in the tenth embodiment, the non-voltage-converting transfer control step includes a step of inhibiting, when the electrical energy is being transferred to the second power supply in the non-voltage-converting state, driving of a high load during a transfer for inhibiting driving of the driven unit that consumes power exceeding power corresponding to electrical energy which can be supplied in the transfer.